Machine for circular grinding



Dec. 5, 1933. A M, REWNGTON 1,938,439

MACHINE FOR CIRCULAR GRINDING Filed June 1, 1931 @W MMM Patented Dec. 5, 1933 UNITED STATES PATENT OFFICE v1,938,439 MACHINE FOR CIRCULAR GRINDING n Application June 1, 193.1. Serial No..541,1`52

Claims.

This invention relates. to the art of machining or grinding a surface disposed transversely of a rotating piece of stock as well as to apparatus for these purposes. 5 It is customary to perform operations of vthis character by causing a tool to travel transversely of the stock at a substantially uniform or unvarying velocity. In so moving, the trace of the tool over the stock follows the coursecf a spiral and the continuously changing relative speed of the stock and tool causes the tool to become less effective as the axis of rotation is approached. Tools suitable for these purposeshave optimum speeds at which they operate with best efficiency and also limiting speeds beyond which satisfactory performance may not be expected. y

To avoid exceeding the maximum speed for the tool these operations arefrequently con-` ducted by rotating the stock ati-a speed which 21) produces the maximum permissible. relative speed at the greatest diameter, but when this is done the tool operates at its optimum speed only through a relatively small portion ,of its travel with the result that the cutting eiciency of the tool is reduced as the axis of rotation is approached. As a reasult of these conditions it has heretofore often been necessary; to take lighter cuts throughout the major portion of the travel of the tool than those which the tool is capable of taking at its optimum speeds, and hence the full efficiency of the tool is not obtained and frequently the time required for the operation is considerably increased. Difficulties of this kind become even greater when the tool employed is of the rotary driven type such as a grindingv wheel. k

For example, in facing circularsaws the` saw is mounted on a turntable `and a rotating grinder is moved back and forth radially of the saw. If the turntable and the grinder rotate at constant speed and thegrinder is moved back and forth between the periphery and center of the saw at uniforml linear velocity, the rate of grinding near the center of the saw is muchless than `near the peripheryv for the reason that the center is moving at a much lower linear velocity. Heretofore it has been customary to adjust the rate of rotation to obtain maximum eiiiciency near the periphery of the saw where therelative movement between grinder and saw is-maximum and consequently the efficiency near the center has been corn-` paratively low.

ObjectsA of this invention are to overcome difiiculties of the character referred to by mairi- .motor speed.

taining ythe speed of the stock relative to the effective portion of the tool substantially constant at the optimum speed for the latter; to provide for simultaneously varying the rotational speed of the stock and the speed of travel 6d of the ltool vto produce a substantially constant relative speed corresponding to the optimum speed for the tool; to provide simple and ei'- cient apparatus for these purposes; and also to provide apparatusy of the class described having an improved construction and relative arrangement of parts.

In the application of the present invention to the aforesaid grinding lof saws for example, the rotation of the turntable is accelerated as the 7o. grinder progresses toward the rcenter of the saw and decelerated as the grinder returnsv toward the periphery, thereby to maintain the relative linear. velocity between saw and grinder, due to their rotation, approximately constant. '11?'75A the progression of Vthe grinder radially of the saw were maintained constant as heretofore this variation in the angular velocity of the saw would result in a decrease inthe pitch of the` feed of the grinder relatively to the sawlthat is a decrease in the vdistance the grinder prograsses` radially of the `savv per vrevolution of the saw) as the grinder advances toward the center of 'the saw, resulting in a progressive decrease in Width of cut per saw revolution and a con- 85 sequenty variation in efiiciency. Consequently'l propose to vary the rate of feed of the grinder radially of the saw at a rate corresponding to the variation in angular velocity of the saw, thereby to maintain approximately constanty the pitch or width of cut as well as the aforesaid relative linear velocity of the saw and grinder. By simultaneously making these two variations in speed, namely the speed of rotation of the turntable and the rate of feed or reciprocation 9,5 of the grinder radially of the saw, a' saw can be .ground in a smallfraction of the rtirneref. quired by the old method, where therate', oi rotation of' the turntable was constantQandthe rate of feed of the grinder was `also constant.

The single ligure of the drawing is a side'elevation of grinding apparatus, some ofthe parts being omitted and others broken away.

In the apparatus selected for illustration` a rotary Work supporting table l0 is connected to the armature shaft of a driving motor 1l. A rheostat 12.v is connected by the conductors 13 and 14 to the field circuit of the motorV to provide a variable resistance for controlling the surf ace 42.

the grinding wheel to move transversely across the upper surface of the work table. 10, preferably substantially along a radius of this Work table. A power cylinder 28 is disposed adjacent the head and fitted with a pistonV 29 having its rod 31 secured to the head 2l by connecting means indicated generally at 32. kPressure fluid for operating the piston 29 is supplied through a pipe 38 to a control valve 34 from which pipes 36and 37 lead to ports at opposite ends of the cylinder. The control Valvev also has the usual discharge connection 38 and is generally of a construction well' known in the art. The delivery of pressure uid from this valve to the cylinder is` arrangedv to be controlled by a plunger .i9 slidably mounted in the valve casing. This plunger normally is pressed. inwardly as by means oi a spring (not shown) to permit full flow ofpressure'fluid delivered' throughthe connection A3,3 alternately to the connections 35 and 37.

Thereciprocable head 2l carriesa cam member 41 havingj a downwardly inclined cam surface 42. A lever 43 is mounted to pivot intermediate its ends in a positi'onvto have the lower end thereof bear against the head or the plunger 3.9,. while the upper end' of this lever carries a roller positioned' to bear'againstthe inclined cam Another4 roller 46' is carried by an arm '47 arranged in position to hold the roller against the cam surface 42. This arm is mounted upon a rotatable shaft. 48 which carries a gear-sector 49, the latter meshing with a pinion 5,1 which is fast to a large gear 52. The rheostat 12 is equipped with, a. pinion 53 mesh,- ing with the large gear 52 and this pinion is adapted, upon rotation to vary the resistance in eld4 circuit of the motor. l

In operation, iluid such as oil is delivered under pressure to the conduit V33 from Ywhich it is. directed by the control valve alternately to opposite rends of the cylinder for operating; the piston and in this vmanner causing the head 21 to reciprocate and `carry the grinding wheel 16 transversely across the surface of a piece oi stock 56 mounted' upon the work table.

The motor 26 is also, operated to, transmit power through the belt 23 and the pulley 22 to the grinding wheelror rotating the latter. As the head reciprocates, the beit is adapted to traverse the, widened face of the pulley 22. The

.motor 11 is alsooperated to set the work table and the stock 56 in rotation. As therotating grinding wheel 16` is advanced across a surface of the rotating piece of stock 5,6 the inclined surface. 42 or" the cam 4I becomesV effective to move the arm tl7`progressively a clockwiseY direction and at the same time to move the lever 143 progressively andv continuously ina countertation of the piece of stock. Conclurently with this action movement of the lever 43 is eiiective continuously and progressively to depress the plunger 39 so as to increase the delivery of pressure luid through the conduit 37. This progressively increases the speed of travel of the grinding wheel 16 as the latter approaches the axis of rotation or Vthe stool: being machined. On the return stroke the lever 43 is actuated in the reverse order progressively to reduce the ow of motive fluid by means of the plunger 39 so as to reduce the speed of travel as the grinding wheel 16 moves outwardly or away from the axis of rotation of. the piece of stock. Likewise the arm 47is effective through the gearing for rotating the gear 53 in a direction opposite to that in which it has just been moved and in this way to Vary the resistance in the eld circuit so as to= decrease the speed of the motor and the rotational speedv of the stock.

'It will be understood that the cam 41 and the moansV operated thereby are so arranged as to maintain the speed of the stock relative to the tool at the points of engagement substantially constant at the optimum speed for the particular tool employed. Asv the tool 16 is driven at a substantially constant speed, it will be evident that thel features of this invention apply also toa tool of the non-rotatable type. While with some tools under certain conditions of operation, it is possible considerably to improve the cutting efficiency and in many cases to approximate at least, if not to maintain` the optimum speed merelyv by varying either the rotational speed l ofthe stock or the speed of travel of the tool,

it is preferred to control both of these factors concurrently, as a large class of operations may beA improved byy following the latter mode of procedure. Moreover, as the speed of travel ofthe tool and also the rotational speed of the stock is controlled bythe position of the cam 41, it will be seen that these speeds are in effect controlled in response to the actual location or position of the tool 16 with respect to the axis of rotation of the stock.

It should be understood that the present disclosure is for the purpose of illustration only and'` that this invention includes all modificationsV and equivalents which fall within the scope of the appended claims.

I claim:

1. Apparatus of the class described comprising a rotatable work support, means for supporting a tool for movement transversely of the work support, operating means for rotating the work support and for causing the tool to travel transversely' thereof, a cam movable with the tool during travel thereof, and a plurality of control means operable by the cam, one of said control t means being effective for substantially continuously and concurrently varying the rotational speed ofthe worksupport and the other of said control means being effective for substantially continuously and concurrently varying the speed of travel ofthe tool to maintain the relative speed of stock carried by the work support and the` tool at points of engagement therebetween substantially constant at the optimumy speed for the tool.

2. Apparatus of the class described comprising a rotatable-work support, a tool, means for supportingv the tool for movement transversely of the work support, operating means for rotating the work support, a power cylinder for causing the tool to travel transversely of the work sup- 'ist port, means responsive to travel of the tool for varying the delivery ot pressure fluid to the power cylinder, and other means fory concurrently varying the speed of theoperatingmeans for the work support, whereby the speed of stock carried by the work support relative to the tool at points of rengagement may be maintained substantially constant at the optimum speedfor the tool.

3. Apparatus of the class described` compris ing a rotatable work'support, a tool, means for supporting the tool for movement transversely of the work support, operating means. for rotating the work support, a power cylinder for causing the tool to travel transversely of the work support, a cam, means responsive to travel of the tool for moving the cam, and control means operable by the cam for substantially continuously and concurrently varying the speed of the operating means and also the delivery of pressure uid to the power cylinder, `whereby the speed of stock carried by the work support relative to the tool at points of engagement therebetween may be maintained substantially constant at the optimum speed for the tool.

4. Apparatus of the class described comprisof the Work support, operating 'means for ro-\ tating the work support, a power cylinder for causing the tool to travel transversely of the;

work support, a cam, control members engageable with the cam and operable thereby concurrently for varying the rate of flow of pressure fluid tothe power cylinder and for varying the speed of said work support, and means responsive to travel of the tool for effecting relative movement of the cam and the control members for actuating the latter.

5. Apparatus of the class described comprising a rotary Work support, a motor for operating said work support, a variable resistance for controlling thespeed of'said motor, a tool, means for yreciprowlting said tool transversely of the work support, a cam, a control member engageable therewith and operable thereby for varying said resistance, and means responsive to movement `of said ltool for eiecting relative movement of said cam and said control member and thereby varying the speed of the work support ALFRED M. REMINGTON. 

